There are three Hobbit movies. This game was released before the third film. The plan was, after the third film was released in theaters, DLC would be released that contained game content that followed along with the third film.
This DLC was cancelled.
As a result, this game follows along with only the first two films in the Hobbit film trilogy. This is inconsistent with Lego Star Wars (I, II, and The Complete Saga) and Lego Lord of the Rings.
It's not a bug per se, but it's certainly an issue with the game. Users considering the purchase may come to PCGW first. Maybe it's worth pointing out in the wiki article?